When a species is trying to make its way in the world, in many cases, the best strategy for survival is clear - a wild bear population hunts fish to feed itself and its offspring, for example, and this will influence how the species evolves over time. But in some cases, a species is presented with two survival strategies, so how does evolution 'decide' between them? In the latest episode of Veritasium, Derek sits down with evolutionary biologist Richard Dawkins to nut out the theory behind evolutionarily stable strategies, and how this inevitably leads to a 50/50 sex ratio.

As a hypothetical, says Dawkins, consider two types of strategies that seabirds could use to feed themselves: the fisher and the pirate. One bird has evolved to catch its own food out of the ocean, while the another has evolved to steal that food away for itself. Both are equally viable strategies, so why do some birds end up as fishers, and others as pirates? And which strategy is the most stable one for a species to evolve towards?

"It depends on what the rest of the population are doing," says Dawkins. "If the whole population is fishing, then it could very well be that an individual could mutate and become a pirate, because there's plenty of fishing going on, and it's easy to steal a fish."

It makes sense then, that because a pirate would have an advantage over a population of fishers, the gene for piracy would spread, and within a few generations, everybody's a pirate. But in this scenario, there are no more fishers to steal from, which means, so long, species. You chose an evolutionary unstable strategy and you should feel ashamed. 

On the other hand, the fishers shouldn't feel so smug, because fishing wasn't a stable strategy either, having been so easily toppled by one mutant bird with a genetic predisposition for piracy. 

When a species is faced with a choice for how to best survive, Dawkins tells Derek, maintaining a healthy ratio between the two is the most stable strategy to ensure its longevity. And perhaps the most famous example of this healthy ratio is the human species' own (give-or-take) 50/50 sex ratio. Watch the latest episode of Veritasium above to find out why and thank your lucky stars that evolution hasn't left you stranded in a world with no potential mates.